Downhole wellbore high power laser heating and fracturing stimulation and methods

ABSTRACT

A system for fracturing a formation comprising a laser surface unit configured to generate a laser beam, a power cable electrically connected to a power source, a fluid line connected to a cooling fluid source, a protective shaft extending into the wellbore, the motor configured to rotate a motor shaft, and the thermal shocking tool comprising a protective case, a rotational shaft connected to the motor shaft, the laser delivery device extending from the rotational shaft configured to transform the laser beam to a focused laser beam operable to increase the temperature of the formation to a fracture temperature, and the cooling system extending from the rotational shaft opposite the laser delivery device configured to introduce the cooling fluid stream onto the formation such that the cooling fluid stream reduces the temperature of the formation such that thermal shocks occur and fractures are formed in the formation.

TECHNICAL FIELD

Disclosed are apparatus and methods for wellbore stimulation. Morespecifically, embodiments related to apparatus and methods thatincorporate lasers for wellbore stimulation applications.

BACKGROUND

Methods for stimulating a wellbore aim to provide a pathway for fluidsto flow from the formation to the wellbore. Hydraulic fracturing is onemethod for stimulating a wellbore. Conventional hydraulic fracturinginjects water at high pressure into the wellbore, which causes fracturesof the formation. In conventional hydraulic fracturing, an explosivecharge is used to perforate the casing and cementing. An explosivecharge is a high impact technology that can cause compaction,deformation of the hole, and sanding and crushing the grains of the rockmaterial. The crushed grains of rock material can be pushed into theformation, blocking the formation and reducing production.

Additionally, the use of water in conventional hydraulic fracturing isincompatible with certain types of formation, such as shale. Water inshale can cause clay swelling, which blocks flow from the formation tothe wellbore.

SUMMARY

Disclosed are apparatus and methods for wellbore stimulation. Morespecifically, embodiments related to apparatus and methods thatincorporate lasers for wellbore stimulation applications.

In a first aspect, a system for fracturing a formation from a wellboreextending into the formation from a surface is provided. The systemincludes a laser surface unit located on the surface, the laser surfaceunit configured to generate a laser beam, a fiber optic cable opticallyconnected to a laser delivery device of a thermal shocking tool, thefiber optic cable configured to transmit the laser beam to the laserdelivery device to produce a focused laser beam, a power cableelectrically connected to a power source on the surface, the power cableconfigured to transmit electrical energy to a motor, a fluid lineconnected to a cooling fluid source on the surface, the fluid lineconfigured to supply a cooling fluid to a cooling system of the thermalshocking tool to produce a cooling fluid stream, a protective shaftextending into the wellbore, wherein the fiber optic cable, the powercable, and the fluid line are contained within the protective shaft, themotor configured to rotate a motor shaft, and the thermal shocking toolphysically connected to the motor. The thermal shocking tool includes aprotective case configured to encompass the laser delivery device andthe cooling system, a rotational shaft connected to the motor shaft suchthat as the motor shaft rotates the rotational shaft rotates, the laserdelivery device extending from the rotational shaft, the laser deliverydevice configured to transform the laser beam to a focused laser beam,wherein the focused laser beam is operable to increase the temperatureof the formation to a fracture temperature, and the cooling systemextending from the rotational shaft opposite the laser delivery device,the cooling system comprising one or more cooling nozzles extendingthrough the protective case such that the one or more cooling nozzlesare configured to introduce the cooling fluid stream onto the formationsuch that the cooling fluid stream reduces the temperature of theformation, where the laser delivery device and the cooling system rotatearound the wellbore as the rotational shaft rotates, where rotation ofthe rotational shaft is configured to alternate between increasing thetemperature of the formation and reducing the temperature of theformation such that thermal shocks occur and fractures are formed in theformation.

In certain aspects, the system further includes a purge nozzle, thepurge nozzle positioned between the surface and the motor, where thepurge nozzle is configured to keep debris from settling on the motor. Incertain aspects, the cooling fluid is selected from the group consistingof nitrogen gas, liquid nitrogen, helium, air, carbon dioxide, andwater. In certain aspects, the fracture temperature is 2000 deg. C. Incertain aspects, the system further includes an acoustic capability. Incertain aspects, the focused laser beam can increase the temperature ofthe formation to the fracture temperature in less than 1 second. Incertain aspects, the laser delivery device can be positioned tointroduce the focused laser beam to the formation at a pre-determinedangle.

In a second aspect, a method for fracturing a formation from a wellboreextending into the formation from a surface is provided. The methodincludes the steps of introducing a focused laser beam to the formationsuch that the focused laser beam is operable to increase the temperatureof the formation to a fracture temperature. The focused laser beam isproduced by a laser delivery device extending from a rotational shaft.The method further includes a step of introducing a cooling fluid streamto the formation such that the cooling fluid stream is operable toreduce the temperature of the formation, where the cooling fluid streamis produced by a cooling system. The cooling system device extendingfrom the rotational shaft opposite from the laser delivery device; androtating the rotational shaft such that the formation is alternatelyintroduced to the focused laser beam and the cooling fluid such thatthermal shocks occur and fractures in the formation are formed.

In certain aspects, the method further includes the steps of generatinga laser beam in a laser surface unit, and transmitting the laser beamfrom the laser surface unit to the laser delivery device through a fiberoptic cable. In certain aspects, the method further includes the stepsof transmitting electrical energy from a power source to a motor througha power cable, and transforming the electrical energy to mechanicalenergy in the motor, such that the mechanical energy rotates a motorshaft, wherein the motor shaft is connected to the rotational shaft suchthat as the motor shaft rotates the rotational shaft rotates. In certainaspects, the method further includes the step of measuring the soundemitted by an acoustic capability.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages will become betterunderstood with regard to the following descriptions, claims, andaccompanying drawings. It is to be noted, however, that the drawingsillustrate only several embodiments and are therefore not to beconsidered limiting of the inventive scope as it can admit to otherequally effective embodiments.

FIG. 1 is a plan view of an embodiment of the laser fracturing tool.

FIG. 2 is a plan view of the laser fracturing tool including the motorand the thermal shocking tool.

FIG. 3 is a plan view of an embodiment of the thermal shocking tool.

FIG. 4 is a pictorial representation of core samples fractured by laser.

DETAILED DESCRIPTION

While the scope will be described with several embodiments, it isunderstood that one of ordinary skill in the relevant art willappreciate that many examples, variations and alterations to theapparatus and methods described are within the scope and spirit of theembodiments. Accordingly, the embodiments described here are set forthwithout any loss of generality, and without imposing limitations. Thoseof skill in the art understand that the inventive scope includes allpossible combinations and uses of particular features described in thespecification. In both the drawings and the detailed description, likenumbers refer to like elements throughout.

Described are an apparatus and methods for fracturing a formation with alaser fracturing tool. The laser fracturing tool can be used toestablish fluid communication between the wellbore and the formation toimprove production of formation fluids. Advantageously, the laserfracturing tool can provide a targeted method of fracturing theformation as compared to a conventional hydraulic fracturing. The laserfracturing tool can be used to target the location of the fracture, suchas targeting the angle and depth of the fracture. In addition, the lasercan be located along fault lines. Advantageously, the rotation of thelaser fracturing tool means the method of fracturing can be implementedaround the entire circumference of the wellbore without the need toreposition the tool. Advantageously, the laser fracturing tool in theabsence of a hydraulic fracturing step. The absence of hydraulicfracturing has environmental advantages as hydraulic fracturing consumesand pollutes large quantities of water. The laser fracturing toolproduces less damage to the rock material of a formation thanconventional hydraulic fracturing.

FIG. 1 is an elevation view of laser fracturing tool 100. Laserfracturing tool 100 is deployed in wellbore 10 of formation 40. Surface30 is the surface of the earth from which wellbore 10 extends. Wellbore10 extends from surface 30 into formation 40. Formation 40 can be anytype of formation composed of any type of rock material. In at least oneembodiment, formation 40 contains limestone. In at least one embodiment,formation 40 contains sandstone. In at least one embodiment, formation40 contains shale. Wellbore 10 can be finished with casing 20 and cement25 for reinforcement.

Laser surface unit 50 can be located on surface 30 near wellbore 10.Laser surface unit 50 can be in optical communication with laserfracturing tool 100 via fiber optic cable 55. Laser surface unit 50 canbe configured to excite energy to a level above the sublimation point offormation 40 to form a laser beam (not shown). The sublimation point offormation 40 can be determined based on the rock material contained information 40, where the rock material controls the sublimation pointwhich then controls the excitation energy of the laser beam. In at leastone embodiment, laser surface unit 50 can be tuned to excite energy todifferent excitation levels as can be required for different formations.Laser surface unit 50 can by any type of laser unit capable ofgenerating a laser beam and introducing said laser beam into a fiberoptic cable. Examples of laser surface unit 50 include lasers ofytterbium, erbium, neodymium, dysprosium, praseodymium, and thuliumions. In at least one embodiment, laser surface unit 50 can be a 5.34-kWytterbium doped multiclad fiber laser.

Fiber optic cable 55 can be any cable containing an optical fibercapable of transmitting a laser beam from laser surface unit 50 to laserfracturing tool 100. Fiber optic cable 55 can include one or moreoptical fibers. In an alternate embodiment, one or more fiber opticcables can provide electrical communication between laser surface unit50 and laser fracturing tool 100. In at least one embodiment, fiberoptic cable 55 provides a path for light from laser surface unit 50 tolaser fracturing tool 100. In at least one embodiment, fiber optic cable55 can conduct a raw laser beam from laser surface unit 50 to laserfracturing tool 100. A “raw laser beam” as used herein refers to a laserbeam that has not been passed through lenses or otherwise focused.

Power source 60 can be located on surface 30 near wellbore 10. Powersource 60 can be in electrical communication with laser fracturing tool100 via power cable 65. Power source 60 can be any apparatus capable ofgenerating electrical energy. Power cable 65 can be any type of cablecapable of transmitting electrical energy to laser fracturing tool 100.

Cooling fluid source 70 can be located on surface 30 near wellbore 10and can provide a cooling fluid to laser fracturing tool 100. Coolingfluid source 70 is in fluid communication with laser fracturing tool 100via fluid line 75, such that the cooling fluid is delivered to laserfracturing tool 100 from cooling fluid source 70. Fluid line 75 can beany type of tube capable of supplying a fluid to laser fracturing tool100. The cooling fluid can include nitrogen gas, liquid nitrogen,helium, air, carbon dioxide, and water. The cooling fluid can beselected based on the rock material of formation 40 and the thermalproperties of the rock material. The temperature gradient desiredbetween the fracture temperature and the cooled temperature, therotation period of the thermal shocking tool, and the efficiency of thecooling fluid in reducing the temperature of the rock material. In atleast one embodiment, one or more fluid lines 75 can be in fluidcommunication with cooling fluid source 70 and laser fracturing tool100.

Fiber optic cable 55, power cable 65, and fluid line 75 can beencompassed in protective shaft 80. Protective shaft 80 can be anymaterial of construction suitable for use in a downhole environmentwithout experiencing mechanical or chemical failure. As used here,“downhole environment” refers to the high operating pressure, highoperating temperature, and fluid conditions that can be found in awellbore extending into a formation.

FIG. 2 is a section view in elevation of one embodiment of laserfracturing tool 100 as understood with reference to FIG. 1. Laserfracturing tool 100 includes motor 200 and thermal shocking tool 300.Power cable 65 is in electrical communication with motor 200, such thatpower cable 65 transmits electrical energy to motor 200. Motor 200 isphysically connected to motor shaft 210. Motor 200 can be any motorcapable of converting electrical energy transmitted by power cable 65into mechanical energy to rotate motor shaft 210 in a downholeenvironment. Motor shaft 210 is physically connected to rotational shaft310 of thermal shocking tool 300.

Fiber optic cable 55 is in optical communication with thermal shockingtool 300. Cooling fluid line 75 is in fluid communication with thermalshocking tool 300.

In at least one embodiment, purge nozzle 220 can be located betweenmotor 200 and surface 30, such that purge nozzle 220 is configured todeliver a fluid to the wellbore. In at least one embodiment, purgenozzle 220 can be located between motor 200 and surface 30 near motor200 such that purge nozzle 220 is operable to deliver the fluid nearmotor 200. In at least one embodiment, purge nozzle 220 delivers thefluid such that the fluid is operable to clean motor 200, such that thepurge fluid from purge nozzle 220 can keep dust and debris from settlingon motor 200. In at least one embodiment, purge nozzle 220 delivers thefluid such that the fluid is operable to direct the produced fluid inwellbore 10. As used here, “produced fluid” refers to the fluid thatflows from the formation into the wellbore due to fracturing of theformation by laser fracturing tool 100. In at least one embodiment, oneor more purge nozzles 220 can be configured in a purge nozzleconfiguration (not shown) such that the purge nozzle configuration isconfigured to deliver the fluid to multiple points in wellbore 10. Thepurge fluid can be any fluid capable of cleaning the motor and directingfluid. Examples of purge fluid can include air and nitrogen gas. Thepurge fluid can be at the ambient temperature of the purge fluid source(not shown). In an alternate embodiment, the purge fluid is from coolingfluid source 70.

FIG. 3 is a section view in elevation of a thermal shocking tool 300with reference to features described in FIG. 2. Thermal shocking tool300 includes protective case 305, rotational shaft 310, cooling system320, and laser delivery device 330.

Protective case 305 surrounds rotational shaft 310, cooling system 320,and laser delivery device 330. Protective case 305 can be formed fromany materials capable of withstanding the downhole environment withoutsuffering mechanical failure. Cooling system 320 and laser deliverydevice 330 can extend into and through protective case 305.

Rotational shaft 310 connected to motor shaft 210 extends throughprotective case 305. Rotational shaft 310 rotates as motor shaft 210rotates as driven by motor 200. Rotational shaft 310 provides an axisaround which cooling system 320 and laser delivery device 330 rotate.Rotational shaft 310 can provide physical support, such as an anchor tocooling system 320 and laser delivery device 330. Cooling system 320 andlaser delivery device 330 are mounted to rational shaft 310 such thatcooling system 320 is opposite laser delivery device 330. As usedherein, “opposite” refers to a position 180 degrees around the axisformed by rotational shaft 310, such that if cooling system 320 extendsperpendicularly from rotational shaft 310 at zero (0) degrees, laserdelivery device extends perpendicularly from rotational shaft 310 atone-hundred eighty (180) degrees. Rotational shaft 310 can be anymaterial of construction suitable for use in a downhole environment thatis rigid enough to provide physical support to cooling system 320 andlaser delivery device 330.

Cooling system 320 can include one or more cooling nozzles 325 as shownin FIG. 3. Cooling nozzles 325 are fluidly connected to fluid line 75,such that the cooled purge fluid is delivered from cooling fluid source70. Cooling system 320 can be configured to introduce the cooling fluidto formation 40 as a cooling fluid stream. The cooling fluid stream isoperable to reduce the temperature formation 40.

Laser delivery device 330 is optically connected to fiber optic cable55. Laser delivery device 330 can be configured to focus the laser beamfrom fiber optic cable 55 to produce a focused beam. In one embodiment,laser delivery device 330 can incorporate the features and details setforth in U.S. Pat. No. 9,217,291.

The focused laser beam is operable to increase the temperature offormation 40. The focused laser beam can be directed to sublimate thecasing and the cement prior to contact formation 40. Advantageously, thefocused laser beam can precisely cut the casing and the cement. Thefocused laser beam can increase the temperature of formation 40 in lessthan one second to a fracture temperature. The fracture temperature canreach 2,000 degrees Celsius (deg C.). The less than one second increasein temperature to the fracture temperature can cause thermal shocks information 40 which results in fractures, microfractures and cracks inthe rock material of formation 40. As used here, “microfractures” refersto fractures in the range from a millimeter to a few centimeters thatcan be used for initiating fractures. As used here, “thermal shocks”refers to the expansion and contraction of the formation rock over atime period on the order of seconds. As thermal shocking tool 300rotates, laser delivery device 330 continuously causes an increase intemperature of formation 40 around the wellbore. While laser deliverydevice 330 increases the temperature of formation 40, cooling system 320decreases the temperature. The cooling fluid stream can be directed atformation 40, such that the cooling fluid stream can reduce thetemperature of the formation to a cooled temperature. The cooledtemperature depends on the fluid used as the cooling fluid stream.

The laser delivery device can include acoustic capability to monitor andrecord the fracturing sound due to the thermal shocking tool. Acousticcapability can include transducers or geophones. Fracturing sound can beused to indicate the fracture length and size. The acoustic capabilitycan be placed above the motor, below the thermal shocking tool, or bothabove the motor and below the thermal shocking tool. Power can besupplied to the acoustic capability from power source 60 (not shown).The acoustic capability can transmit the measurements directly to thesurface or can be stored and retrieved after the laser fracturing.

EXAMPLE Example 1

A dry core sample measuring 2″×2″ of Berea and limestone was obtained. A3 kW power laser was used to produce a continuous laser beam of 0.35inches. The laser beam was turned on for four (4) seconds before beingswitched off. Fractures immediately formed in the core sample. Air, atroom temperature, was used as the cooling fluid stream on one side ofthe core sample to orient the fractures. As can be seen in FIG. 4,fractures formed in the core sample.

Although the technology has been described in detail, it should beunderstood that various changes, substitutions, and alterations can bemade hereupon without departing from the inventive principle and scope.Accordingly, the scope of the embodiments should be determined by thefollowing claims and their appropriate legal equivalents.

The singular forms “a,” “an,” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances can or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed as from one particular value to anotherparticular value. When such a range is expressed, it is to be understoodthat another embodiment is from the one particular value to the otherparticular value, along with all combinations within said range.

Throughout this application, where patents or publications arereferenced, the disclosures of these references in their entireties areintended to be incorporated by reference into this application, in orderto more fully describe the state of the art, except when thesereferences contradict the statements made here.

As used here and in the appended claims, the words “comprise,” “has,”and “include” and all grammatical variations thereof are each intendedto have an open, non-limiting meaning that does not exclude additionalelements or steps.

What is claimed is:
 1. A system for fracturing a formation from awellbore extending into the formation from a surface, the systemcomprising: a laser surface unit, the laser surface unit located on thesurface, the laser surface unit configured to generate a laser beam; afiber optic cable, the fiber optic cable optically connected to a laserdelivery device of a thermal shocking tool, the fiber optic cableconfigured to transmit the laser beam to the laser delivery device toproduce a focused laser beam; a power cable, the power cableelectrically connected to a power source on the surface, the power cableconfigured to transmit electrical energy to a motor; a fluid line, thefluid line connected to a cooling fluid source on the surface, the fluidline configured to supply a cooling fluid to a cooling system of thethermal shocking tool to produce a cooling fluid stream; a protectiveshaft, the protective shaft extending into the wellbore, wherein thefiber optic cable, the power cable, and the fluid line are containedwithin the protective shaft; the motor, the motor configured to rotate amotor shaft; and the thermal shocking tool physically connected to themotor, the thermal shocking tool comprising: a protective case, theprotective case configured to encompass the laser delivery device andthe cooling system, a rotational shaft, the rotational shaft connectedto the motor shaft such that as the motor shaft rotates the rotationalshaft rotates, the laser delivery device extending from the rotationalshaft, the laser delivery device configured to transform the laser beamto a focused laser beam, wherein the focused laser beam is operable toincrease the temperature of the formation to a fracture temperature, andthe cooling system, the cooling system extending from the rotationalshaft opposite the laser delivery device, the cooling system comprisingone or more cooling nozzles extending through the protective case suchthat the one or more cooling nozzles are configured to introduce thecooling fluid stream onto the formation such that the cooling fluidstream reduces the temperature of the formation, wherein the laserdelivery device and the cooling system rotate around the wellbore as therotational shaft rotates, wherein rotation of the rotational shaft isconfigured to alternate between increasing the temperature of theformation and reducing the temperature of the formation such thatthermal shocks occur and fractures are formed in the formation.
 2. Thesystem of claim 1 further comprises a purge nozzle, the purge nozzlepositioned between the surface and the motor, where the purge nozzle isconfigured to keep debris from settling on the motor.
 3. The system ofclaim 1, wherein the cooling fluid is selected from the group consistingof nitrogen gas, liquid nitrogen, helium, air, carbon dioxide, andwater.
 4. The system of claim 1, wherein the fracture temperature is2000 deg. C.
 5. The system of claim 1 further comprising an acousticcapability.
 6. The system of claim 1, wherein the focused laser beam canincrease the temperature of the formation to the fracture temperature inless than 1 second.
 7. The system of claim 1, wherein the laser deliverydevice can be positioned to introduce the focused laser beam to theformation at a pre-determined angle.
 8. A method for fracturing aformation from a wellbore extending into the formation from a surface,the method comprising the steps of: introducing a focused laser beam tothe formation such that the focused laser beam is operable to increasethe temperature of the formation to a fracture temperature, wherein thefocused laser beam is produced by a laser delivery device, the laserdelivery device extending from a rotational shaft; introducing a coolingfluid stream to the formation such that the cooling fluid stream isoperable to reduce the temperature of the formation, wherein the coolingfluid stream is produced by a cooling system, the cooling system deviceextending from the rotational shaft opposite from the laser deliverydevice; and rotating the rotational shaft such that the formation isalternately introduced to the focused laser beam and the cooling fluidsuch that thermal shocks occur and fractures in the formation areformed.
 9. The method of claim 8, further comprising the steps of:generating a laser beam in a laser surface unit; and transmitting thelaser beam from the laser surface unit to the laser delivery devicethrough a fiber optic cable.
 10. The method of claim 8, furthercomprising the steps of: transmitting electrical energy from a powersource to a motor through a power cable; and transforming the electricalenergy to mechanical energy in the motor, such that the mechanicalenergy rotates a motor shaft, wherein the motor shaft is connected tothe rotational shaft such that as the motor shaft rotates the rotationalshaft rotates.
 11. The method of claim 8, wherein the cooling fluid isselected from the group consisting of nitrogen gas, liquid nitrogen,helium, air, carbon dioxide, and water.
 12. The method of claim 8,wherein the fracture temperature is 2000 deg. C.
 13. The method of claim8 further comprising the step of measuring the sound emitted by anacoustic capability.
 14. The method of claim 8, wherein the focusedlaser beam can increase the temperature of the formation to the fracturetemperature in less than 1 second.
 15. The method of claim 8, whereinthe laser delivery device can be positioned to introduce the focusedlaser beam to the formation at a pre-determined angle.